の can be a number of things. It is one of the characters out of the forty-six that exist in the hiragana series. It is part of some vocabulary words as well. However, it is most often used as a grammatical particle placed between nouns or phrases to show their relationship. For example: Showing a specific location: アメリカのケンタッキー州。。。 The state of Kentucky in America... Showing that "Kentucky" is a state in "America," you have to list the place names in order from largest to smallest. Here is another example of that: 日本の徳島県の徳島市。。。 Tokushima city in Tokushima prefecture in Japan. の　is also used to show possession. 私のペンです。 It's my pen. I hope this is clear enough. Please let me know if you have any more questions.